Many industrial operations produce waste materials consisting of hydrocarbon contaminated solid substrates which must be decontaminated prior to disposal in an environmentally acceptable way. Similarly, hydrocarbon contaminated substrates that had been disposed of previously under less stringent environmental regulations and accidental spills of hydrocarbon materials have led to hydrocarbon contaminated soils which must be treated to substantially reduce the hydrocarbon contaminant present in the soils to acceptable levels. Thus, the ability to economically separate hydrocarbon contaminants from solid substrates, such as soil, is extremely important not only in cleaning up previously contaminated soils but also in separating hydrocarbon contaminated industrial solid wastes into reusable and disposable fractions.
Various techniques are known in the art for treating hydrocarbon containing substrates. These include solvent extraction, water washing, incineration, flotation and the like. As useful as these various techniques may be, each has its own debits. For example, water washing techniques known in the art typically result in the formation of hydrocarbon and water emulsions that are extremely difficult to break. Treatment of soils with hydrocarbons solvents involves higher materials and separation costs than when water is used. Incineration is costly and requires control of noxious emissions. Floatation is limited in its applicability to specific soil types and a narrow range of contaminant types. Therefore, there remains a need for a method of separating hydrocarbon contaminants from soil substrates that is more economical and versatile.